In a semiconductor manufacturing process, there is widely used a plasma processing device that performs a plasma process for the purpose of depositing or etching a thin film. Examples of the plasma processing device include a plasma CVD (Chemical Vapor Deposition) device for performing a thin film deposition process and a plasma etching device for performing an etching process.
The plasma processing device includes a processing chamber for processing a target substrate, a stage on which the target substrate is mounted in the processing chamber, a gas supply system for introducing a processing gas required in a plasma reaction into the processing chamber, and so forth. The plasma processing device further includes a plasma generation mechanism for supplying electromagnetic energy such as microwaves or RF waves into the processing chamber to convert the processing gas in the processing chamber to plasma, a voltage applying mechanism for applying a bias voltage to the target stage and accelerating ions in the plasma toward the target substrate mounted on the target stage, and so forth.
In the plasma processing device, due to the variations in the inner surface temperature of the processing chamber, it is sometimes the case that the processing accuracy of target substrates varies even if a plasma process is repeated under the same processing condition. Description will be made by taking a plasma etching device as an example. For example, if a plasma etching process is performed after a lapse of a period of time from when a previous plasma etching process is performed, there may be a case where the etching rate of the first target substrate of an initial lot (the first lot) becomes lower than the etching rate of a subsequent target substrate. Presumably, this is because the temperature of the inner surface of the processing chamber is decreased due to the leaving a certain amount of time after the execution of a previous plasma etching process and because the next plasma etching process is performed in that state.
In the related art, as a solution to this problem, there is known a method in which, as disclosed in Patent Document 1, seasoning is carried out prior to performing a plasma process for the target substrates of the first lot. The seasoning means that the temperature of the inner surface of the processing chamber is increased by loading a dummy wafer on a stage and performing a plasma generating process before a plasma process for the first lot is performed. After the temperature of the inner surface of the processing chamber is increased, a normal plasma process is performed. According to this method, it is presumably possible to prevent a decrease in the etching rate even when the target substrate of the first lot are processed after the temperature of the inner surface of the processing chamber is decreased.